1200 miles on a clean break	Try getting that back in its box
10-speed joining pin…	…with its eight and nine-speed siblings

Shimano CN-7801 Chain £29.95 (116 links)

Shimano chains tend to get a bad press. In the main this has to be because the joining system can prove troublesome for the home mechanic. This is despite the fact that the system is about as simple as could be devised – which is where it may be going wrong.

Before returning to the subject, let’s look at the specification of Shimano’s top-end road chain. Wearing, of course, the Dura-Ace name on the zinc-plated flanks of its outer plates, the ‘Super-Narrow’ CN-7801 chain is designed to work with 10 speed cassettes and may not shift properly between the wider-spaced chainrings of a nine-speed setup. Weight is a claimed 280g for 116 links. The side plates are plain and unadorned by any indents of other shaping of the sort that might be expected to improve shifting performance.

The ‘Link Pin’ has a tapered guide tip, two identifying grooves and a deep waist. This is followed by a ridge, with another on the far end of what constitutes the ‘working’ end of the pin. The ridges are designed to prevent the side plates from pulling off once the pin has been installed. They are precisely dimensioned. As the ridge next to the waist passes through the side plate, it does not permanently deform the hole, which instead stretches elastically to allow its passage and then returns to its correct dimension.

Installation is done by first removing links to make the chain the desired length. The new chain will have inner plates at one free end and outer at the other. It may have a captive Link Pin ready to press through. If not, use one of the two spare pins provided. The guide tip is dimensioned to pass easily through the four plates. A chain tool is required to press the second section of pin through. This is where some skill is needed; the pin must be pressed through far enough to push the waist-side ridge past the plate without risking pushing the other ridge through its own plate.

Once this has been done, the guide tip can be snapped off using pliers. At this point the join will be stiff, because the outer plates have been pressed together by the chain tool. They must be freed off, which can be done either with an old-school chain tool with secondary teeth designed for the job, or by holding the chain either side of the join with the thumb pressed against the pin. Applying lateral force to the chain will move the outer plates apart.

Grooved end in first	Ridges match width of outer plates
Use pliers to snap off tip	Strangely pleasing to view

Frankly, this part of the process is a bit of a lash-up even with a decent chain tool. Even the pressing-through bit is fraught with risk and likely to end badly if done by the heavy-handed. However, if done well it produces a very reliable join in what can only be described as a long-lived chain. The example on test has done some 1200 miles including the 2007 London-Paris Cycle Tour and, after four or five proper cleans, shows no sign of stretch or corrosion. It shifts beautifully on Dura-Ace or SRAM cassettes and runs smoothly enough to go unnoticed at all times.

For 2009, Shimano is expected to introduce a new tool-free joining link that will do away with the Link Pin. Not before time, some will say, especially as there are several excellent formats available for other equally effective drive chains. Others will remember with fondness a system that only the competent could operate with real confidence.